/*
 * The contents of this file are subject to the terms 
 * of the Common Development and Distribution License 
 * (the "License").  You may not use this file except 
 * in compliance with the License.
 * 
 * You can obtain a copy of the license at 
 * glassfish/bootstrap/legal/CDDLv1.0.txt or 
 * https://glassfish.dev.java.net/public/CDDLv1.0.html. 
 * See the License for the specific language governing 
 * permissions and limitations under the License.
 * 
 * When distributing Covered Code, include this CDDL 
 * HEADER in each file and include the License file at 
 * glassfish/bootstrap/legal/CDDLv1.0.txt.  If applicable, 
 * add the following below this CDDL HEADER, with the 
 * fields enclosed by brackets "[]" replaced with your 
 * own identifying information: Portions Copyright [yyyy] 
 * [name of copyright owner]
 */
// Copyright (c) 1998, 2007, Oracle. All rights reserved.  
package oracle.toplink.essentials.descriptors;

import java.math.*;
import java.io.*;
import java.util.*;
import oracle.toplink.essentials.mappings.*;
import oracle.toplink.essentials.internal.helper.*;
import oracle.toplink.essentials.queryframework.*;
import oracle.toplink.essentials.expressions.*;
import oracle.toplink.essentials.exceptions.*;
import oracle.toplink.essentials.internal.descriptors.OptimisticLockingPolicy;
import oracle.toplink.essentials.internal.sessions.ObjectChangeSet;
import oracle.toplink.essentials.internal.sessions.AbstractRecord;
import oracle.toplink.essentials.internal.sessions.UnitOfWorkImpl;
import oracle.toplink.essentials.internal.sessions.AbstractSession;

/**
 * <p><b>Purpose</b>: Used to allow a single version number to be used for optimistic locking.
 *
 * @since TOPLink/Java 2.0
 */
public class VersionLockingPolicy implements OptimisticLockingPolicy, Serializable {
    protected DatabaseField writeLockField;
    protected int lockValueStored;
    protected ClassDescriptor descriptor;
    protected transient Expression cachedExpression;
    public final static int IN_CACHE = 1;
    public final static int IN_OBJECT = 2;

    /**
     * PUBLIC:
     * Create a new VersionLockingPolicy.  Defaults to
     * storing the lock value in the cache.
     */
    public VersionLockingPolicy() {
        super();
        storeInCache();
    }

    /**
     * PUBLIC:
     * Create a new VersionLockingPolicy.  Defaults to
     * storing the lock value in the cache.
     * @param fieldName specifies the field name for the write
     * lock field.
     */
    public VersionLockingPolicy(String fieldName) {
        this(new DatabaseField(fieldName));
    }

    /**
     * PUBLIC:
     * Create a new VersionLockingPolicy.  Defaults to
     * storing the lock value in the cache.
     * @param the write lock field.
     */
    public VersionLockingPolicy(DatabaseField field) {
        this();
        setWriteLockField(field);
    }

    /**
     * INTERNAL:
     * Add update fields for template row.
     * These are any unmapped fields required to write in an update.
     */
    public void addLockFieldsToUpdateRow(AbstractRecord databaseRow, AbstractSession session) {
        if (isStoredInCache()) {
            databaseRow.put(getWriteLockField(), null);
        }
    }

    /**
     * INTERNAL:
     * This method adds the lock value to the translation row of the
     * passed in query. depending on the storage flag, the value is
     * either retrieved from the cache of the object.
     */
    public void addLockValuesToTranslationRow(ObjectLevelModifyQuery query) {
        Object value;
        if (isStoredInCache()) {
            value = query.getSession().getIdentityMapAccessor().getWriteLockValue(query.getPrimaryKey(), query.getObject().getClass());
        } else {
            value = lockValueFromObject(query.getObject());
        }
        if (value == null) {
            if (query.isDeleteObjectQuery()) {
                throw OptimisticLockException.noVersionNumberWhenDeleting(query.getObject(), query);
            } else {
                throw OptimisticLockException.noVersionNumberWhenUpdating(query.getObject(), query);
            }
        }
        query.getTranslationRow().put(getWriteLockField(), value);
    }

    /**
     * INTERNAL:
     * When given an expression, this method will return a new expression with
     * the optimistic locking values included.  The values are taken from the
     * passed in database row.  This expression will be used in a delete call.
     */
    public Expression buildDeleteExpression(DatabaseTable table, Expression mainExpression, AbstractRecord row) {
        //use the same expression as update
        return buildUpdateExpression(table, mainExpression, row, null);
    }

    /**
     * INTERNAL:
     * Returns an expression that will be used for both the update and
     * delete where clause
     */
    protected Expression buildExpression() {
        ExpressionBuilder builder = new ExpressionBuilder();

        return builder.getField(getWriteLockField()).equal(builder.getParameter(getWriteLockField()));
    }

    /**
     * INTERNAL:
     * When given an expression, this method will return a new expression
     * with the optimistic locking values included.  The values are taken
     * from the passed in database row.  This expression will be used in
     * an update call.
     */
    public Expression buildUpdateExpression(DatabaseTable table, Expression mainExpression, AbstractRecord row, AbstractRecord row2) {
        if (cachedExpression == null) {
            cachedExpression = buildExpression();
        }
        if (getWriteLockField().getTableName().equals(table.getName())) {
            return mainExpression.and(cachedExpression);
        }
        return mainExpression;
    }

    /**
     * INTERNAL:
     * Clone the policy
     */
    public Object clone() {
        try {
            return super.clone();
        } catch (CloneNotSupportedException e) {
            return null;
        }
    }

    /**
     * INTERNAL:
     * This method compares two writeLockValues.
     * The writeLockValues should be non-null and of type Number.
     * Returns:
     * -1 if value1 is less (older) than value2;
     *  0 if value1 equals value2;
     *  1 if value1 is greater (newer) than value2.
     * Throws:
     *  NullPointerException if the passed value is null;
     *  ClassCastException if the passed value is of a wrong type.
     */
    public int compareWriteLockValues(Object value1, Object value2) {
        BigDecimal bigDecimalValue1, bigDecimalValue2;
        if(value1 instanceof BigDecimal) {
            bigDecimalValue1 = (BigDecimal)value1;
        } else {
            bigDecimalValue1 = new BigDecimal(((Number)value1).longValue());
        }
        if(value2 instanceof BigDecimal) {
            bigDecimalValue2 = (BigDecimal)value2;
        } else {
            bigDecimalValue2 = new BigDecimal(((Number)value2).longValue());
        }
        return bigDecimalValue1.compareTo(bigDecimalValue2);
    }

    /**
     * INTERNAL:

     * Return the default version locking filed java type, default is BigDecimal

     */
    protected Class getDefaultLockingFieldType() {
        return ClassConstants.BIGDECIMAL;

    }

    /**
     * INTERNAL:
     * This is the base value that is older than all other values, it is used in the place of
     * null in some situations.
     */
    public Object getBaseValue() {
        return new BigDecimal(0);
    }

    /**
     * INTERNAL:
     */
    protected ClassDescriptor getDescriptor() {
        return descriptor;
    }

    /**
     * INTERNAL:
     * returns the initial locking value
     */
    protected Object getInitialWriteValue(AbstractSession session) {
        return new BigDecimal(1);
    }

    /**
     * INTERNAL:
     * This method gets the write lock value from either the cache or
     * the object stored in the query.  It then returns the new incremented value.
     */
    protected Object getNewLockValue(ModifyQuery query) {
        Class objectClass = query.getDescriptor().getJavaClass();
        Number value;
        Number newWriteLockValue = null;
        if (isStoredInCache()) {
            value = (Number)query.getSession().getIdentityMapAccessor().getWriteLockValue(((WriteObjectQuery)query).getPrimaryKey(), objectClass);
        } else {
            value = (Number)lockValueFromObject(((ObjectLevelModifyQuery)query).getObject());
        }
        if (value == null) {
            throw oracle.toplink.essentials.exceptions.OptimisticLockException.noVersionNumberWhenUpdating(((ObjectLevelModifyQuery)query).getObject(), (ObjectLevelModifyQuery)query);
        }

        // Increment the value, this goes to the database
        newWriteLockValue = incrementWriteLockValue(value);
        return newWriteLockValue;
    }

    /**
     * INTERNAL:
     * This method returns any of the fields that are not mapped in
     * the object.  In the case of the value being stored in the
     * cache, a vector with one value is returned.  In the case
     * of being stored in the object, an empty vector is returned.
     */
    protected Vector getUnmappedFields() {
        Vector fields = new Vector(1);
        if (isStoredInCache()) {
            fields.addElement(getWriteLockField());
        }
        return fields;
    }

    /**
     * INTERNAL:
     * Return the value that should be stored in the identity map.
     * If the value is stored in the object, then return a null.
     */
    public Object getValueToPutInCache(AbstractRecord row, AbstractSession session) {
        if (isStoredInCache()) {
            return row.get(getWriteLockField());
        } else {
            return null;
        }
    }

    /**
     * PUBLIC:
     * Return the number of versions different between these objects.
     * @param currentValue the new lock value
     * @param domainObject the object containing the version to be compared to
     * @param primaryKeys a vector containing the primary keys of the domainObject
     * @param session the session to be used with the comparison
     */
    public int getVersionDifference(Object currentValue, Object domainObject, Vector primaryKeys, AbstractSession session) {
        Number writeLockFieldValue;
        Number newWriteLockFieldValue = (Number)currentValue;

        // 2.5.1.6 if the write lock value is null, then what ever we have is treated as newer.
        if (newWriteLockFieldValue == null) {
            return 0;//merge it as either the object is new or being forced merged.
        }

        if (isStoredInCache()) {
            writeLockFieldValue = (Number)session.getIdentityMapAccessor().getWriteLockValue(primaryKeys, domainObject.getClass());
        } else {
            writeLockFieldValue = (Number)lockValueFromObject(domainObject);
        }
        if (writeLockFieldValue == null) {
            writeLockFieldValue = new BigDecimal(0);// the object is not in the cache so assume this is a new object
        }
        if (!(writeLockFieldValue instanceof BigDecimal)) {
            writeLockFieldValue = new BigDecimal(writeLockFieldValue.longValue());
        }
        if (!(newWriteLockFieldValue instanceof BigDecimal)) {
            newWriteLockFieldValue = new BigDecimal(newWriteLockFieldValue.longValue());
        }
        return ((BigDecimal)newWriteLockFieldValue).subtract((BigDecimal)writeLockFieldValue).intValue();
    }

    /**
       * INTERNAL:
       * Return the write lock field.
       */
    public DatabaseField getWriteLockField() {
        return writeLockField;
    }

    /**
     * PUBLIC:
     * Return the field name of the field that stores the write lock value.
     */
    public String getWriteLockFieldName() {
        return getWriteLockField().getQualifiedName();
    }

    /**
     * INTERNAL:
     * Retrun an expression that updates the write lock
     */
    public Expression getWriteLockUpdateExpression(ExpressionBuilder builder) {
        return ExpressionMath.add(builder.getField(writeLockField.getName()), 1);
    }

    /**
     * INTERNAL:
     * This method will return the optimistic lock value for the object
     */
    public Object getWriteLockValue(Object domainObject, java.util.Vector primaryKey, AbstractSession session) {
        Number writeLockFieldValue;
        if (isStoredInCache()) {
            writeLockFieldValue = (Number)session.getIdentityMapAccessor().getWriteLockValue(primaryKey, domainObject.getClass());
        } else {
            writeLockFieldValue = (Number)lockValueFromObject(domainObject);
        }
        return writeLockFieldValue;
    }

    /**
     * INTERNAL:
     * adds 1 to the value passed in
     */
    protected Number incrementWriteLockValue(Number numberValue) {
        BigDecimal writeLockValue;

        if (numberValue instanceof BigDecimal) {
            writeLockValue = (BigDecimal)numberValue;
        } else {
            writeLockValue = new BigDecimal(numberValue.doubleValue());
        }

        return writeLockValue.add(new BigDecimal(1));
    }

    /**
     * INTERNAL:
     * It is responsible for initializing the policy;
     */
    public void initialize(AbstractSession session) {
        DatabaseMapping mapping = mappingFromLockField();
        if (mapping == null) {
            if (isStoredInObject()) {
                throw OptimisticLockException.mustHaveMappingWhenStoredInObject(descriptor.getJavaClass());
            } else {
                return;
            }
        }
        if (mapping.isReadOnly()) {
            throw DescriptorException.mappingCanNotBeReadOnly(mapping);
        } else {
            if (isStoredInCache()) {
                session.getIntegrityChecker().handleError(DescriptorException.mustBeReadOnlyMappingWhenStoredInCache(mapping));
            }
        }
    }

    /**
     * INTERNAL:
     * It is responsible for initializing the policy properties;
     */
    public void initializeProperties() {
        DatabaseField dbField = getWriteLockField();

        descriptor.buildField(dbField);
        if (dbField.getType() == null) {
            //set the default type
            dbField.setType(getDefaultLockingFieldType());

        }
        Enumeration enumtr = this.getUnmappedFields().elements();
        while (enumtr.hasMoreElements()) {
            DatabaseField lockField;
            lockField = (DatabaseField)enumtr.nextElement();
            descriptor.getFields().addElement(lockField);
        }
    }

    /**
     * INTERNAL:
     * Update the parent write lock value if the unit of works has been incremented.
     */
    public boolean isChildWriteLockValueGreater(AbstractSession session, java.util.Vector primaryKey, Class original, ObjectChangeSet changeSet) {
        if (isStoredInCache()) {
            // If this uow changed the object the version must be updated,
            // we can check this by ensuring our value is greater than our parent's.
            Number writeLockValue = (Number)changeSet.getWriteLockValue();
            Number parentValue = (Number)session.getIdentityMapAccessor().getWriteLockValue(primaryKey, original);
            if ((parentValue != null) && (!(parentValue instanceof BigDecimal))) {
                parentValue = new BigDecimal(parentValue.longValue());
            }
            if ((writeLockValue != null) && (!(writeLockValue instanceof BigDecimal))) {
                writeLockValue = new BigDecimal(writeLockValue.longValue());
            }
            if (writeLockValue != null) {// This occurs if the object was deleted
                if ((parentValue == null) || (((BigDecimal)parentValue).compareTo((BigDecimal)writeLockValue) == -1)) {
                    return true;
                }
            }
        }
        return false;
    }

    /**
     * INTERNAL:
     * Update the parent write lock value if the unit of works has been incremented.
     */
    public boolean isChildWriteLockValueGreater(UnitOfWorkImpl uow, java.util.Vector primaryKey, Class original) {
        if (isStoredInCache()) {
            // If this uow changed the object the version must be updated,
            // we can check this by ensuring our value is greater than our parent's.
            Number writeLockValue = (Number)uow.getIdentityMapAccessor().getWriteLockValue(primaryKey, original);
            Number parentValue = (Number)uow.getParent().getIdentityMapAccessor().getWriteLockValue(primaryKey, original);
            if ((parentValue != null) && (!(parentValue instanceof BigDecimal))) {
                parentValue = new BigDecimal(parentValue.longValue());
            }
            if ((writeLockValue != null) && (!(writeLockValue instanceof BigDecimal))) {
                writeLockValue = new BigDecimal(writeLockValue.longValue());
            }
            if (writeLockValue != null) {// This occurs if the object was deleted
                if ((parentValue == null) || (((BigDecimal)parentValue).compareTo((BigDecimal)writeLockValue) == -1)) {
                    return true;
                }
            }
        }
        return false;
    }

    /**
     * INTERNAL:
     * Compares the value with the value from the object (or cache).
     * Will return true if the object is newer.
     */
    public boolean isNewerVersion(Object currentValue, Object domainObject, java.util.Vector primaryKey, AbstractSession session) {
        Number writeLockFieldValue;
        Number newWriteLockFieldValue = (Number)currentValue;

        // 2.5.1.6 if the write lock value is null, then what ever we have is treated as newer.
        if (newWriteLockFieldValue == null) {
            return true;
        }

        if (isStoredInCache()) {
            writeLockFieldValue = (Number)session.getIdentityMapAccessor().getWriteLockValue(primaryKey, domainObject.getClass());
        } else {
            writeLockFieldValue = (Number)lockValueFromObject(domainObject);
        }
        if (!(writeLockFieldValue instanceof BigDecimal)) {
            writeLockFieldValue = new BigDecimal(writeLockFieldValue.longValue());
        }
        if (!(newWriteLockFieldValue instanceof BigDecimal)) {
            newWriteLockFieldValue = new BigDecimal(newWriteLockFieldValue.longValue());
        }
        if ((writeLockFieldValue != null) && (((BigDecimal)newWriteLockFieldValue).compareTo((BigDecimal)writeLockFieldValue) != 1)) {
            return false;
        }
        return true;
    }

    /**
     * INTERNAL:
     * Compares the value from the row and from the object (or cache).
     * Will return true if the object is newer than the row.
     */
    public boolean isNewerVersion(AbstractRecord databaseRow, Object domainObject, java.util.Vector primaryKey, AbstractSession session) {
        Number writeLockFieldValue;
        Number newWriteLockFieldValue = (Number)databaseRow.get(getWriteLockField());
        if (isStoredInCache()) {
            writeLockFieldValue = (Number)session.getIdentityMapAccessor().getWriteLockValue(primaryKey, domainObject.getClass());
        } else {
            writeLockFieldValue = (Number)lockValueFromObject(domainObject);
        }
        if (!(writeLockFieldValue instanceof BigDecimal)) {
            writeLockFieldValue = new BigDecimal(writeLockFieldValue.longValue());
        }
        if (!(newWriteLockFieldValue instanceof BigDecimal)) {
            newWriteLockFieldValue = new BigDecimal(newWriteLockFieldValue.longValue());
        }
        if ((writeLockFieldValue != null) && (((BigDecimal)newWriteLockFieldValue).compareTo((BigDecimal)writeLockFieldValue) != 1)) {
            return false;
        }
        return true;
    }

    /**
     * PUBLIC:
     * Return true if the lock value is stored in the cache.
     */
    public boolean isStoredInCache() {
        return lockValueStored == IN_CACHE;
    }

    /**
     * PUBLIC:
     * Return true if the lock value is stored in the object.
     */
    public boolean isStoredInObject() {
        return lockValueStored == IN_OBJECT;
    }

    /**
     * INTERNAL:
     * retrieves the lock value from the object.
     */
    protected Object lockValueFromObject(Object domainObject) {
        return getDescriptor().getObjectBuilder().getBaseValueForField(getWriteLockField(), domainObject);
    }

    /**
     * INTERNAL:
     * returns the mapping from the writelock field.
     * returns null if not found
     */
    protected DatabaseMapping mappingFromLockField() {
        return descriptor.getObjectBuilder().getMappingForField(getWriteLockField());
    }

    /**
     * INTERNAL:
     * Only applicable when the value is stored in the cache.  Will merge with the parent unit of work.
     */
    public void mergeIntoParentCache(UnitOfWorkImpl uow, Vector primaryKey, Object object) {
        if (isStoredInCache()) {
            Object parentValue = uow.getParent().getIdentityMapAccessor().getWriteLockValue(primaryKey, object.getClass());
            uow.getIdentityMapAccessor().updateWriteLockValue(primaryKey, object.getClass(), parentValue);
        }
    }

    /**
     * INTERNAL:
     */
    public void setDescriptor(ClassDescriptor descriptor) {
        this.descriptor = descriptor;
    }

    /**
     * PUBLIC:
     * Set whether to store the lock in the cache or in the object.
     * @param isStoredInCache set this to true if you would like to store lock in the cache and set it
     * to false if you would like to store it in the object.
     */
    public void setIsStoredInCache(boolean isStoredInCache) {
        if (isStoredInCache) {
            storeInCache();
        } else {
            storeInObject();
        }
    }

    /**
     * INTERNAL:
     * This method must be included in any locking policy.
     * Put the initial writelock value into the modifyRow.
     */
    public void setupWriteFieldsForInsert(ObjectLevelModifyQuery query) {
        Object lockValue = getInitialWriteValue(query.getSession());
        ObjectChangeSet objectChangeSet = query.getObjectChangeSet();
        if (objectChangeSet != null) {
            objectChangeSet.setInitialWriteLockValue(lockValue);
        }
        updateWriteLockValueForWrite(query, lockValue);
    }

    /**
     * INTERNAL:
     * Update the row, object and change set with the version value.
     * This handles the version being mapped in nested aggregates, writable or read-only.
     */
    protected void updateWriteLockValueForWrite(ObjectLevelModifyQuery query, Object lockValue) {
        query.getModifyRow().put(getWriteLockField(), lockValue);
        ObjectChangeSet objectChangeSet = query.getObjectChangeSet();
        if (objectChangeSet != null) {
            objectChangeSet.setWriteLockValue(lockValue);
        }

        // CR#3173211
        // If the value is stored in the cache or object, there still may
        // be read-only mappings for it, so the object must always be updated for
        // any writable or read-only mappings for the version value.
        // Reuse the method used for returning as has the same requirements.
        AbstractRecord record = getDescriptor().getObjectBuilder().createRecord(1);
        record.put(getWriteLockField(), lockValue);
        getDescriptor().getObjectBuilder().assignReturnRow(query.getObject(), query.getSession(), record);
        if (query.getSession().isUnitOfWork() && (((UnitOfWorkImpl)query.getSession()).getUnitOfWorkChangeSet() != null)) {
            if (objectChangeSet == null) {
                // For aggregate collections the change set may be null, as they use the old commit still.
                objectChangeSet = (ObjectChangeSet)((UnitOfWorkImpl)query.getSession()).getUnitOfWorkChangeSet().getObjectChangeSetForClone(query.getObject());
            }
            query.getQueryMechanism().updateChangeSet(getDescriptor(), objectChangeSet, record, query.getObject());
        }
    }

    /**
     * ADVANCED:
     * Set the write lock field.
     * This can be used for advanced field types, such as XML nodes, or to set the field type.
     */
    public void setWriteLockField(DatabaseField writeLockField) {
        this.writeLockField = writeLockField;
    }

    /**
     * PUBLIC:
     * Set the write lock field name.
     * @param writeLockFieldName the name of the field to lock against.
     */
    public void setWriteLockFieldName(String writeLockFieldName) {
        setWriteLockField(new DatabaseField(writeLockFieldName));
    }

    /**
     * PUBLIC:
     * Configure the version lock value to be stored in the cache.
     * This allows for the object not to require to store its version value as an attribute.
     * Note: if using a stateless model where the object can be passed to a client and then
     * later updated in a different transaction context, then the version lock value should
     * not be stored in the cache, but in the object to ensure it is the correct value for
     * that object.  This is the default.
     */
    public void storeInCache() {
        lockValueStored = IN_CACHE;
    }

    /**
     * PUBLIC:
     * Configure the version lock value to be stored in the object.
     * The object must define a mapping and an attribute to store the version value.
     * Note: the value will be updated internally by TopLink and should not be updated
     * by the application.
     */
    public void storeInObject() {
        lockValueStored = IN_OBJECT;
    }

    /**
     * INTERNAL:
     * This method updates the modify row, and the domain object
     * with the new lock value.
     *
     * #see this method in VersionLockingPolicy
     */
    public void updateRowAndObjectForUpdate(ObjectLevelModifyQuery query, Object domainObject) {
        Object lockValue = getNewLockValue(query);
        if (isStoredInCache()) {
            query.getSession().getIdentityMapAccessor().updateWriteLockValue(query.getPrimaryKey(), domainObject.getClass(), lockValue);
        }
        updateWriteLockValueForWrite(query, lockValue);
    }

    /**
     * INTERNAL:
     * This method updates the modify row with the old lock value.
     */
    public void writeLockValueIntoRow(ObjectLevelModifyQuery query, Object domainObject) {
        Object lockValue = getWriteLockValue(domainObject, query.getPrimaryKey(), query.getSession());
        query.getModifyRow().put(getWriteLockField(), lockValue);
        if (isStoredInCache()) {
            query.getSession().getIdentityMapAccessor().updateWriteLockValue(query.getPrimaryKey(), domainObject.getClass(), lockValue);
        }
    }

    /**
     * INTERNAL:
     * Check the row count for lock failure.
     */
    public void validateDelete(int rowCount, Object object, DeleteObjectQuery query) {
        if (rowCount <= 0) {
            throw OptimisticLockException.objectChangedSinceLastReadWhenDeleting(object, query);
        }
    }

    /**
     * INTERNAL:
     * Check the row count for lock failure.
     */
    public void validateUpdate(int rowCount, Object object, WriteObjectQuery owner) {
        if (rowCount <= 0) {
            throw OptimisticLockException.objectChangedSinceLastReadWhenUpdating(object, owner);
        }
    }

    /**
     * INTERNAL:
     * Prepare fetch group for read query
     */
    public void prepareFetchGroupForReadQuery(FetchGroup fetchGroup, ObjectLevelReadQuery query) {
        //version stored in object, add the version attribute to the fetch group attribute list
        if (isStoredInObject()) {
            String verAttributeName = descriptor.getObjectBuilder().getMappingForField(writeLockField).getAttributeName();
            fetchGroup.addAttribute(verAttributeName);
        } else {//stored in cache, add the version field to the select fields
            if (!query.getAdditionalFields().contains(writeLockField)) {
                query.addAdditionalField(writeLockField);
            }
        }
    }
}
